Solar battery module manufacturing method

ABSTRACT

Provided is a process of producing a solar battery module  1  including plural solar battery cells  4  sealed by a resin  5  between a transparent panel  2  of the light reception surface side and a back face panel  3 , which is characterized by arranging plural solar battery cells  4  at a prescribed interval and mutually connecting them to each other by a conductor  8 ; arranging a first sealing resin sheet  12  substantially covering the entire surface of the transparent panel  2  of the light reception surface side between the transparent panel  2  of the light reception surface side and the solar battery cells  4 ; arranging a second sealing resin sheet  10  substantially covering the entire surface of the back face panel  3  between the back face panel  3  and the solar battery cells  4 ; arranging sealing resin sheet pieces  18, 19  which are thicker than the solar battery cells  4  at a space  9  between the solar battery cells  4  so as to be sandwiched by the first sealing resin sheet  12  and the second sealing resin sheet  10 ; discharging air between the transparent panel  2  of the light reception surface side and the back face panel  3 ; and heating the resin  5  for melting and then cooling down it for sealing. According to this, when the plural solar battery cells  4  are arranged and sealed by the resin  5 , breakage of the solar battery cells  4  can be prevented from occurring.

TECHNICAL FIELD

The present invention relates to a process of producing a solar batterymodule. In particular, the invention relates to a process of producing asolar battery module including solar battery cells sealed by a resinbetween a transparent panel of the light reception surface side and aback face panel.

BACKGROUND ART

In recent years, consciousness of the environmental protection has beenincreasing, and importance of the solar photovoltaic power generation ismore increasing. A solar battery cell is sandwiched by protectivematerials, sealed by a transparent resin, and then provided for useoutdoors as a solar battery module. As the transparent resin forsealing, an ethylene-vinyl acetate copolymer (hereinafter sometimesabbreviated as “EVA”) or the like is used, and sealing is conducted bysandwiching the resin between the protective material and the solarbattery cell, heat melting and then solidifying it. In order toefficiently arrange the solar battery cell and wiring it, it ispreferable that plural solar battery cells are sealed within a singlesolar battery module.

Also, recently, the place at which a solar battery is set up isdiversified, and the solar battery is used not only on the roof of abuilding but also at a wall portion. In the case of use at a wall, thesolar battery is not only installed on an outer wall, but also it isemployed to construct the wall itself by a solar battery module. At thistime, if a space is provided among plural solar battery cells and thefront and back surfaces of the solar battery are formed of a transparentmaterial, it becomes possible to prepare a daylighting type solarbattery module capable of taking light in the inside of the wall.

Japanese Utility Model Registration No. 2,500,974 describes a laminatecomposed of two plate-like bodies bonded via two adhesive sheets so asto sandwich a solar battery between the two adhesive sheets, wherein asheet piece having a thickness substantially equal to the solar batteryis sandwiched into a space formed between the adhesive sheets in theoutside of the solar battery. It is described that according to such aconstruction, it is possible to make the thickness of thecircumferential edge portion of the laminate uniform and to preventpeeling from occurring because the moisture hardly invades the foregoingspace from the outside. It is described to use EVA as the adhesive sheetand to use a sheet glass for the plate-like bodies on the both surfaces.

JP-A-59-022978 describes a caulking adhesive sheet for solar batterymodule containing an ethylene-based copolymer and an organic peroxide,the both surfaces of which are provided with an embossed pattern. It isdescribed that since the subject adhesive sheet has an embossed pattern,it can prevent blocking of the sheet from occurring and has excellentdeaeration properties in the modulation stage, thereby hardly generatingair bubbles. In the working examples of this patent document, there isdescribed a lamination method in which the temperature is raised to 150°C. in the reduced pressure state in a vacuum laminator, the pressurereduction is continued at 150° C. for one hour, cooling is performed,and the pressure reduction is then stopped.

JP-A-09-036405 describes a laminated solar battery module prepared byputting a photovoltaic power element between a front face member and aback face member via a sealing resin to form a laminate, maintaining thelaminate at a degree of vacuum of 5 Torr or lower for from 5 to 40minutes, subjecting the laminate to thermocompression bonding at adegree of vacuum of 5 Torr or lower, and after the subjectthermocompression bonding, cooling the laminate. It is described that bythermocompression bonding under such conditions, a module which hardlygenerates peeling of the surface member and hardly generates residualair bubbles is provided. It is also described that by inserting anon-woven fabric between the solar battery cell and the sealing materialresin and releasing the air present in the laminate through gaps in thenon-woven fabric, a problem of the generation of residual air bubblescan be improved.

JP-A-61-069179 describes a process of producing a solar battery panelincluding lamination process of deaerating a solar battery panellaminate composed of a solar battery cell laminated between a coverglass and a back face material via a filler by a double vacuum system,heating, then applying pressure, wherein EVA is used as the filler, anda double vacuum chamber is held at a specific temperature range for aspecific period of time. It is described that by conducting thelamination under specific temperature conditions, the whole of EVA canbe crosslinked without causing foaming and yellowing. According to theconditions described in the working examples thereof, when thetemperature of the board surface in the heater side has reached 140° C.,vacuum compression bonding is conducted, a crosslinking reaction isperformed at 148° C., cooling is performed to 50° C. or lower, and thecompression for bonding is then released.

However, in connecting plural cells to each other and sandwiching thembetween two panels, followed by performing thermocompression bonding andsealing, it was difficult to avoid breakage of the solar battery cells.In particular, in the case where the number of cells is large and thearea of the entire module is large, a large load is likely non-uniformlyapplied, and the breakage of a part of cells which receive an excessiveload was unavoidable. Since the plural cells are mutually connected inseries within the module, if one cell is broken, a series of cells to beconnected do not accomplish the function. In the case where the breakageof cell occurs, not only the appearance is impaired, but also aperformance of power generation is largely lowered, and therefore, theproduct must be discarded as a defective. Accordingly, a sealing methodwhich hardly causes the breakage of cell as far as possible is beingdemanded.

A first invention has been made for the purpose of solving such aproblem and is aimed to provide a process of producing a solar batterymodule which, when plural solar battery cells are arranged and sealed bya transparent resin, can prevent breakage of the solar battery cells.

The foregoing prior patent document describes that the solar batterycells are sealed using an EVA sheet containing a crosslinking agent.And, according to the method described in the foregoing prior patentdocument, even when the temperature is raised to proceed with thecrosslinking reaction, the laminate was placed under high vacuum,thereby continuing strong compression in the vertical direction by theatmospheric pressure.

However, at high temperatures at which the crosslinking reaction canproceed, the sealing resin becomes a liquid the viscosity of which hasbeen lowered. Thus, when the laminate is strongly compressed in thevertical direction, there was a possibility that not only the resin isflowed out from the edge of the laminate, but also the solar batterycells move with the transfer of the resin. If the resin is flowed out,or the solar battery cells move, there was a possibility that not onlythe appearance is deteriorated, but also the wiring connected to thecells is broken, and therefore, improvements were desired. Nevertheless,if the lamination is performed without a pressure reduction operation,air bubbles likely remain in the product, leading to deterioration ofthe appearance, too.

A second invention has been made for the purpose of solving such aproblem and is aimed to provide a process of producing a solar batterymodule having a good appearance, which can inhibit remaining of airbubbles, movement of solar battery cells, or flowing out of the sealingresin from the edge.

DISCLOSURE OF THE INVENTION

The first invention is a process of producing a solar battery moduleincluding plural solar battery cells sealed by a resin between atransparent panel of the light reception surface side and a back facepanel, which is characterized by arranging plural solar battery cells ata prescribed interval and mutually connecting them to each other by aconductor; arranging a first sealing resin sheet substantially coveringthe entire surface of the transparent panel of the light receptionsurface side between the transparent panel of the light receptionsurface side and the solar battery cells; arranging a second sealingresin sheet substantially covering the entire surface of the back facepanel between the back face panel and the solar battery cells; arrangingsealing resin sheet pieces having a thickness thicker than that of thesolar battery cells at a space between the solar battery cells so as tobe sandwiched by the first sealing resin sheet and the second sealingresin sheet; discharging air between the transparent panel of the lightreception surface side and the back face panel; and heating the resinfor melting and then cooling down it for sealing.

By arranging sealing resin sheet pieces having a thickness thicker thanthat of the solar battery cells at a space between the solar batterycells, when the internal pressure is reduced, a load by the atmosphericpressure from both the front and back surfaces is not applied directlyto the solar battery cells, and the foregoing sheet pieces receive thatload. And, when the temperature rises, the resin is softened, thethickness of the sheet pieces to which a load has been applied isreduced, and the cells or the portion of the conductor connected to thecells is brought into contact with the upper and lower sealing resinsheets. At that time, since the resin sheets are entirely softened, theload is not locally applied, and it is possible to bring the cells orthe conductor connected to the cells into intimate contact with thesoftened sealing resin sheets such that the former is embedded in thelatter. In this way, it is possible to prevent cell breakage in thefirst pressure reduction step.

At this time, it is preferable that the thickness of the sealing resinsheet pieces is thicker than the sum total value of the thickness of thesolar battery cells and the thickness of the conductor. It is preferablethat the thickness of the sealing resin sheet pieces is at least 0.3 mmthicker than the thickness of the solar battery cells. It is preferablethat the width of the sealing resin sheet pieces is narrower than thewidth of the space; and it is more preferable that the width of theforegoing sealing resin sheet pieces is from 0.1 to 0.95 times the widthof the foregoing space. It is also preferable that a space is arrangedbetween the sealing resin sheet pieces, and the internal air isdischarged therethrough. Also, it is preferable that the sealing resinsheets are made of at least one resin selected from the group consistingof an ethylene-vinyl acetate copolymer, polyvinyl butyral, andpolyurethane.

The second invention is a process of producing a solar battery moduleincluding a solar battery cell sealed by a resin between a transparentpanel of the light reception surface side and a back face panel, whichis characterized in that the sealing resin is made of a crosslinkablethermoplastic resin, a first sealing resin sheet substantially coveringthe entire surface of the transparent panel of the light receptionsurface side is arranged between the transparent panel of the lightreception surface side and the solar battery cell, a second sealingresin sheet substantially covering the entire surface of the back facepanel is arranged between the back face panel and the solar batterycell, the assembly is introduced into a sealing treatment vessel, andthe sealing operation including respective steps of a step of reducingthe pressure in the sealing treatment vessel at a temperature at whichthe thermoplastic resin is not melted (step 1); a step in which thetemperature is raised to the vicinity of or higher than the meltingpoint of the thermoplastic resin in the reduced-pressure state (step 2);a step in which the pressure in the sealing treatment vessel is raised(step 3); a step in which the temperature is raised to a temperaturerange where a crosslinking reaction proceeds, thereby proceeding withthe crosslinking reaction (step 4); and a step in which cooling isperformed (step 5) is carried out.

In sealing the solar battery cells by a resin, first of all, byperforming a pressure reduction operation, it is possible to inhibit theremaining of air bubbles in the sealing resin. Further, when thetemperature is raised to the vicinity of or higher than the meltingpoint, thereby melting or softening the sealing resin and the pressureis raised by reducing the degree of vacuum, it is possible to prevent aphenomenon that an excessive pressure is applied in the verticaldirection in the state that the sealing resin is molten or softened.Moreover, even when the melt viscosity of the sealing resin becomes lowfor the purpose of proceeding with the crosslinking reaction, since ahigh pressure is not applied in the vertical direction, it is possibleto inhibit movement of the cells or flowing out of the resin.

At this time, it is preferable that in the step 1, the pressure isreduced to 0.01 MPa or lower. It is preferable that when the meltingpoint of the foregoing thermoplastic resin is defined as Tm, thetemperature as reached in the temperature-rising operation of the step 2is (Tm−20) ° C. or higher and (Tm+50)° C. or lower. It is preferablethat in the step 3, the temperature at which the pressure is raised is120° C. or lower. It is preferable that in the step 3, the temperaturerising is simultaneously carried out while raising the pressure in theforegoing sealing treatment vessel. It is preferable that in the step 3,a ratio of the pressure-rising rate (MPa/min) to the temperature-risingrate (° C./min) is from 0.001 to 0.1 (MPa/° C.). Also, it is preferablethat in the step 3, the pressure in the sealing treatment vessel israised, and cooling is then once performed; and in the step 4, thetemperature is raised to a temperature range where the crosslinkingreaction proceeds. It is also preferable that in the step 4, thecrosslinking reaction is made to proceed while keeping the pressure inthe foregoing sealing treatment vessel at 0.05 MPa or more and theatmospheric pressure or lower.

It is a preferred embodiment of the invention that the foregoing solarbattery module is a solar battery module including plural solar batterycells sealed by a resin, and the plural solar battery cells are arrangedat a prescribed interval and mutually connected to each other by aconductor. Also, it is suitable that the foregoing thermoplastic resinis at least one resin selected from the group consisting of anethylene-vinyl acetate copolymer, polyvinyl butyral, and polyurethane.

In the foregoing first and second inventions, it is suitable that atleast one of the transparent panel of the light reception surface sideand the back face panel is made of a tempered glass or a double strengthglass. Also, it is a preferred embodiment that the produced solarbattery module is a daylighting type solar battery module.

The invention will be described below in detail with reference to thedrawings. FIG. 1 is a cross-sectional schematic view of a solar batterymodule of the invention. FIG. 2 is a cross-sectional schematic view of alaminate under reduced pressure in the step 1. FIG. 3 is across-sectional schematic view of a laminate in the way of temperaturerising by heating in the step 2. FIG. 4 is a cross-sectional schematicview of a laminate after cooling in the step 5.

A solar battery module 1 obtained by the production process of theinvention is one in which a solar battery cell 4 is sealed by a resin 5between a transparent panel 2 of the light reception surface side and aback face panel 3. Though the number of the solar battery cell 4 to besealed in the solar battery module 1 may be one, it is preferable thatplural solar battery cells 4 are sealed. Usually, a light receptionsurface 6 and a back face 7 of the adjacent solar battery cells 4 areconnected to each other via a conductor 8. A cross-sectional schematicview of that case is illustrated in FIG. 1.

As the solar battery cell 4 to be used in the invention, cells ofvarious solar batteries such as monocrystalline silicon solar batteries,polycrystalline silicon solar batteries, amorphous silicon solarbatteries, and compound semiconductor solar batteries can be used. Thesesolar battery cells are a thin plate generally having a thickness of 1mm or less, and more generally 0.5 mm or less and in many cases, are aquadrangle having sides of 5 cm or more. With respect to the material oftheir substrates, semiconductor substrates of silicon, germanium, etc.,glass substrates, metal substrates, and so on can be used. In the caseof a silicon substrate, although thinning is desired in view of a demandfrom the cost standpoint, it is rigid and brittle so that it is likelybroken especially at the time of sealing. Accordingly, it is quitemeaningful to employ the production process of the first invention.

The number of the solar battery cell 4 to be sealed in the single solarbattery module 1 is not particularly limited but may be one. In thatcase, a wiring is merely connected to the outside from the solar batterycell 4. However, when the number of the solar battery cell 4 to besealed in the single solar battery module 1 is increased, air bubblesare liable to be generated, and in the case where the solar batterycells 4 move during the sealing operation, a problem is likelyencountered from the standpoint of appearance. Accordingly, in the casewhere plural solar battery cells 4 are sealed in the single solarbattery module 1, it is quite profitable to employ the productionprocess of the second invention. When the number of the solar batterycell 4 to be sealed in the single solar battery module 1 is increased, arate of defective caused due to the breakage of the solar battery cell 4rises, and therefore, it is quite profitable to employ the productionprocess of the first invention. Accordingly, it is preferable that 10 ormore, and suitably 30 or more solar battery cells 4 are arranged in thesingle solar battery module 1.

The distance between the adjacent solar battery cells 4 is notparticularly limited. Though the adjacent solar battery cells 4 may comeclose to each other, the distance therebetween is usually 1 mm or more.In the case where the distance is less than this, the adjacent solarbattery cells 4 come into contact with each other so that cell breakagemay be possibly caused during sealing. By increasing the distance, thedaylighting amount is also increased during the use as a daylightingtype solar battery module. Therefore, the distance is suitably 5 mm ormore, more suitably 10 mm or more, and further suitably 30 mm or more.In the case of employing the production process of the first invention,the distance between the adjacent solar battery cells 4 is usually 5 mmor more. In the case where the distance is less than this, it becomesdifficult to arrange a sealing resin sheet piece 11 in a space 9 betweenthe solar battery cells 4 so that the sealing resin sheet piece 11 maypossibly damage the solar battery cells 4 or the conductor 8 duringsealing.

In the case where plural solar battery cells 4 are sealed, it ispreferable that the plural solar battery cells 4 are arranged via aspace 9 having a prescribed width and mutually connected to each otherby the conductor 8. At this time, the adjacent solar battery cells 4 areconnected to each other by the conductor 8 between the light receptionsurface 6 and the back face 7, and a number of solar battery cells 4 areconnected in the series system. The connection of the light receptionsurface 6 or back face 7 to the conductor 8 is performed using aconductive binding material such as solder. Also, for the purpose ofefficiently collecting a generated current, it is preferable that acurrent collection pattern is formed on the light reception surface 6using a conductive paste, etc. and conducted with the conductor 8.

Though the conductor 8 is also called an interconnector, its material isnot particularly limited, and copper wires and the like are used. Sincethe conductor 8 is arranged while being sandwiched between thetransparent panel 2 of the light reception surface side and the backface panel 3, it is preferred to use a thin ribbon-like conductor 8, andits thickness is usually 0.5 mm or less, and suitably 0.3 mm or less.Also, it is generally 0.05 mm or more. It is preferable that the bindingmaterial such as solder is previously coated on the conductor 8 becausethe connecting work becomes easy. In the state that the conductor 8 isconnected, though the height from the surface of the solar battery cell4 to the highest portion of the conductor 8 is scattered depending uponthe place, it may possibly become approximately 0.5 mm thicker than thethickness of the conductor 8.

With respect to the material of the transparent panel 2 of the lightreception surface side, it is only required that it is transparentagainst sunlight, and besides glass, polycarbonate resins, acrylicresins, and the like can be used, too. However, when the durability,hardness, flame retardancy, etc. are taken into consideration, it ispreferred to use glass. Since a structural member having a large area isoften constructed, the glass is more preferably a tempered glass or adouble strength glass. In the case where the area is large, sincethermal cracks caused due to an increase of the temperature by sunshine,etc. are liable to be generated, it is also suitable from thisstandpoint to use a tempered glass or a double strength glass. Since thetempered glass or double strength glass is produced by heating andquenching a float plate glass, the generation of a certain strain isinevitable. Because of a warp of glass as thus formed, an excessive loadis likely applied to a part of the solar battery cells at the time ofsealing, and therefore, it is quite profitable to employ the productionprocess of the first invention which can prevent cell cracks fromoccurring. Also, because of a warp of glass as thus formed, it isdifficult to make the transparent panel 2 of the light reception surfaceside completely parallel to the back face panel 3 at the time ofsealing, air bubbles are liable to remain, and transfer of the moltenresin is liable to occur at the same time. Accordingly, it is quiteprofitable to employ the production process of the second inventionwhich can inhibit remaining of air bubbles and inhibit transfer of themolten resin.

The tempered glass as referred to herein is one in which a surfacecompression stress thereof is enhanced by thermal treatment and includesnot only general tempered glasses usually having a surface compressionstress of from 90 to 130 MPa but also super tempered glasses usuallyhaving a surface compression stress of from 180 to 250 MPa. Also, thedouble strength glass is one usually having a surface compression stressof from 20 to 60 MPa. The double strength glass is preferable from thestandpoint of the matter that it is free from a phenomenon that whenbroken, it becomes small pieces and drops. That is, in the case where asheet glass having a surface compression stress of 20 MPa or more isused, it is quite profitable to employ the production processes of theinvention. Here, the surface compression stress of the sheet glass is avalue measured according to JIS R3222.

Although the back face panel 3 may be not always transparent, so far asit is used for a daylighting type solar battery module, it is betterthat the back face panel 3 is transparent against sunlight. Also, forthe same reasons as in the transparent panel 2 of the light receptionside, it is preferred to use a glass, especially a tempered glass or adouble strength glass.

The material of the glass is not particularly limited, and a soda limeglass is suitably used. Above all, a high transmittance glass (so-calledwhite sheet glass) is suitably used for the transparent panel 2 of thelight reception surface side. The super vision glass is a soda limeglass having a low content of iron and having a high lighttransmittance. Also, as the glass of the back face side 3, a soda limeglass having a relatively high content of iron (so-called blue sheetglass) is useful, and besides, a heat reflecting glass and a heatabsorbing glass are also preferable depending upon applications. Also, afigured glass having an embossed pattern formed on the surface thereofand the like can be used, and these glasses may be tempered. Thethickness of the glass panel is not particularly limited but when usedas a structural member, is preferably 3 mm or more, and more preferably5 mm or more. In using such a thick glass panel, an influence of its ownweight is large so that in superimposing a glass panel on the cellbefore laminating, the cell may be possibly broken. Therefore, it isquite profitable to employ the production process of the firstinvention. Also, in using such a thick glass panel, it is difficult tocorrect a warp, and therefore, it is quite profitable to employ theproduction process of the second invention. The thickness of the glasspanel is usually 20 mm or less. Also, though the area of the glass isadjusted depending upon applications, in the case where it is 1 m² ormore, it is quite profitable to employ the production processes of theinvention.

With respect to the material of the resin 5, the resin is notparticularly limited so far as it is transparent and has adhesiveness orflexibility. One kind of resin selected from the group consisting of anethylene-vinyl acetate copolymer (EVA), polyvinyl butyral, andpolyurethane is suitably used. At this time, it is preferable from thestandpoints of strength and durability that the resin is a crosslinkedresin. In the production process of the second invention, the rawmaterial of the resin 5 is a crosslinkable thermoplastic resin, andespecially a resin in which a crosslinking reaction proceeds by heating.Such a resin is sandwiched in the form of a sheet between thetransparent panel 2 of the light reception surface side and the backface panel 3, heat melted to proceed with a crosslinking reaction, andthen cooled for solidification, thereby sealing the solar battery cell4. By using a resin which is crosslinked by heating, it is possible tomake the durability or adhesiveness excellent. The crosslinkablethermoplastic resin is not particularly limited so far as it proceedswith the crosslinking reaction at the time of heating. One kind of resinselected from the group consisting of an ethylene-vinyl acetatecopolymer (EVA), polyvinyl butyral, and polyurethane is suitably used.For example, when the resin is EVA, by blending it with a crosslinkingagent and heating the blend, it is possible to perform crosslinking; andwhen the resin is polyurethane, by making an isocyanate group react witha hydroxyl group, it is possible to perform crosslinking.

In the case of polyurethane, since the crosslinking reaction proceeds ata relatively low temperature, the polyurethane is suitable in the caseof using a resin plate having low heat resistance for at least one ofthe transparent panel of the light reception surface side and the backface panel. Also, since the polyurethane has excellent flexibility, too,even in the case of combining a glass with a material having a largelydifferent coefficient of thermal expansion such as plastics and usingfor the transparent panel of the light reception surface side and theback face panel, it hardly generates peeling and therefore, is suitable.Further, the polyurethane has excellent penetration strength, too.

Of crosslinkable thermoplastic resins, it is suitable to use athermoplastic resin containing a crosslinking agent. At this time, thethermoplastic resin is not particularly limited so far as it proceedswith a crosslinking reaction when heated together with the crosslinkingagent. An ethylene-vinyl acetate copolymer (EVA), which is excellent intransparency, flexibility, durability, etc., is most suitably used.

The sealing resin sheet is sandwiched between the transparent panel 2 ofthe light reception surface side and the back face panel 3, is heatmelted, and then cooled for solidification, thereby sealing the solarbattery cells 4. The sealing resin sheet is preferably an EVA resincontaining a crosslinking agent. In this case, by heat melting it toproceed with the crosslinking reaction and then cooling, it is possibleto perform sealing with crosslinked EVA. As EVA in the sealing resinsheet, one having a melting point as measured by the DSC method of from50 to 80° C. is preferable from the viewpoint of a balance betweentransparency and shape retention.

The sealing resin sheet properly embossed on one or both surfacesthereof is preferable because blocking can be prevented, and remainingof air bubbles is readily inhibited. A suitable depth of embossing isfrom 10 to 100 μm, and when the embossing is excessively deep, airbubbles may possibly rather remain. The sheet thickness is preferablyfrom 0.2 to 2 mm and can be adjusted by using a single sheet or bysuperimposing plural sheets.

The sealing operation method according to the production process of theinvention will be described below. First of all, a second sealing resinsheet 10 is superimposed on the back face panel 3 so as to substantiallycover the entire surface thereof. The thickness of the second resinsheet 10 is preferably 0.4 mm or more, and more preferably 0.8 mm ormore. Also, it is usually 3 mm or less. By setting the thickness at acertain value or more, it is possible to efficiently absorb an impact,thereby effectively protecting the solar battery cells 4. Also, when awarp is present in the substrate as in the case of using a temperedglass or a double strength glass for the back face panel 3 or thetransparent panel 2 of the light reception surface side, it ispreferable that the thickness is set at a certain value or more becausethe warp can be absorbed. The second sealing resin sheet 10 may be alaminate of plural raw material sheets.

The solar battery cell 4 is placed on the second sealing resin sheet 10.At this time, it is suitable that plural solar battery cells 4 mutuallyconnected to each other in the manner as described previously are placedand put in order lengthwise and breadthwise as the need arises. In thiscase, the previously connected solar battery cells 4 may be placed; thesolar battery cells 4 may be connected on the second sealing resin sheet10; or the solar battery cells 4 a part of which is connected may beplaced, with the remainder being then connected.

Subsequently, in the case where plural solar battery cells 4 are sealed,it is preferable that a sealing resin sheet piece 11 thicker than thethickness of the solar battery cells 4 is arranged in a space 9 betweenthe solar battery cells 4 such that it is sandwiched between the firstsealing resin sheet 12 and the second sealing sheet 10. By arranging thesealing resin sheet piece 11 thicker than the thickness of the solarbatter cells 4 in the space 9 between the solar battery cells 4, whenthe internal pressure is reduced, a load by the atmospheric pressurefrom the front and back surfaces is not applied directly to the solarbattery cells 4, and the sealing sheet piece 11 receives that load. And,when the temperature rises, the resin is softened, the thickness of thesealing resin sheet piece 11 to which a load has been applied isreduced, and the cells or the portion of the conductor connected to thecells is brought into contact with the upper and lower sealing resinsheets. At that time, since the resin sheets are entirely softened, theload is not locally applied, and it is possible to bring the cells orthe conductor connected to the cells into intimate contact with thesoftened sealing resin sheets such that the former is embedded in thelatter. In this way, it is possible to prevent cell cracks in thepressure reduction step.

In particular, when the number of the solar battery cells 4 to be sealedin the single solar battery module 1 is increased, a rate of defectivecaused due to the breakage of the solar battery cell 4 rises, andtherefore, it is quite profitable to arrange the subject sealing resinsheet piece 11. Also, in the case where a tempered glass or a doublestrength glass having a large warp is used as a material of thetransparent panel 2 of the light reception surface side or the back facepanel 3, an excessive load is likely applied to a part of the solarbattery cells at the time of sealing, and therefore, it is preferred toarrange the subject sealing resin sheet piece 11 which can prevent cellcracks from occurring.

When the conductor 8 is present in the space 9, this sealing resin sheetpiece 11 is usually placed in the state that it is placed on theconnector 8. By arranging the conductor 8 and the sealing resin sheetpiece 11 such that they are superimposed, due to an action to hold theconductor 8, it becomes hard for the solar battery cells 4 to moveduring melting the resin, and therefore, such is more preferable.Although it is not necessary to arrange the sealing resin sheet piece 11in all of the spaces 9 between the adjacent solar battery cells 4, it ispreferred to arrange them in all of the spaces 9 because the transfer ofthe molten resin less occurs, and it becomes harder for air bubbles togenerate. Further, it is also preferred to arrange the sealing resinsheet piece 11 in the surrounding margin of the solar battery module 1because the edge can be surely sealed.

The thickness of the sealing resin sheet piece 11 is preferably at least0.3 mm thicker than the thickness of the solar battery cell 4, and morepreferably at least 0.6 mm thicker than that. Also, at this time, it ispreferable that the thickness of the sealing resin sheet piece 11 isthicker than the sum total value of the thickness of the solar batterycells 4 and the thickness of the conductor 8. By employing such athickness, it is possible to prevent a phenomenon that an excessive loadis applied to a portion to which the load is most likely applied. Inthis case, it is more preferable that the thickness is at least 0.2 mmthicker than the foregoing sum total value. In the case where thesealing resin sheet piece 11 is a construction in which plural sealingresin sheets are laminated, it is only required that the thickness ofthe thickest portion (a portion where the number of sheets to belaminated is large) meets the foregoing conditions.

It is preferable that the width of the sealing resin sheet piece 11 tobe arranged is narrower than the width of the foregoing space 9. This isbecause the sealing resin sheet pieces 11 thicker than the solar batterycells 4 become easy to spread over the whole of the space 9 in a uniformthickness. In the case where the molten resin transfers over a widerange, the solar battery cells 4 may possibly move with the transfer ofthe molten resin. The width is adjusted while taking into considerationthe thickness of the solar battery cells 4 or the sealing resin sheetpieces 11, the area of the space 9, and the like and is suitably from0.1 to 0.95 times the width of the space 9. More suitably, the width is0.3 times or more and 0.9 times or less. When the width exceeds 0.95times, not only the arranging operation becomes difficult, but also thesolar battery cell 4 or the conductor 8 may possibly be broken at thetime of reducing the pressure. Conversely, when it is 0.1 times or less,the molten resin may possibly become difficult to spread uniformly.

Also, it is preferable that a space is arranged between the sealingresin sheet pieces 11, thereby discharging the internal airtherethrough. By securing a passage for positively discharging theinternal air, it is possible to inhibit remaining of air bubbles and toproduce a solar battery module having a good appearance. At this time,in the case where the sealing resin sheet piece 11 is constructed of alaminate of plural sealing resin sheets, it is only required that in atleast one sheet thereof, a space is arranged between the sealing resinsheet pieces, thereby discharging the internal air therethrough. In thecase where the sealing resin sheet pieces 11 are arranged intersected,it is possible to discharge the internal air through a portion having athin total thickness other than the intersecting portions.

In this way, after placing the sealing resin sheet pieces 11, the firstsealing resin sheet 12 is placed thereon. The thickness of the firstresin sheet 12 is preferably 0.4 mm or more, and more preferably 0.8 mmor more. Also, though the thickness is usually 3 mm or less, the lighttransmittance is lowered even slightly in proportion to an increase ofthe thickness. Therefore, the thickness is more preferably 2 mm or less.An effect for protecting the solar battery cells 4 and an effect forabsorbing a warp of the substrate are the same as in the case of thesecond sealing resin sheet 10.

Finally, the transparent panel 2 of the light reception surface side isplaced, thereby completing a laminate 13 before sealing. Usually, thetransparent panel 2 of the light reception surface side and the backface panel 3 have the same planar shape, and the first sealing resinsheet 12 and the second sealing resin sheet 10 have substantially thesame planar shape as the preceding shape. According to the demands onthe post processing and the like, in the case where the shape of thetransparent panel 2 of the light reception surface side is differentfrom that of the back face panel 3, the first sealing resin sheet 12 andthe second sealing resin sheet 10 are arranged on the entire surface ofthe overlapping portion therebetween. In the foregoing description,after placing the back face panel 3 in advance in the lower position,the superimposing operation is carried out. However, after placing thetransparent panel 2 of the light reception surface side in advance inthe lower position, the first sealing resin sheet 12, the solar batterycells 4, the sealing resin sheet pieces 11, the second sealing resinsheet 10, and the back face panel 3 may be superimposed in this order.

Thereafter, the air between the transparent panel 2 of the lightreception surface side and the back face panel 3 is discharged, andheating is performed to melt the resin, followed by cooling for sealing.At this time, it is preferable that heating is performed to melt theresin, thereby proceeding with the crosslinking reaction, followed bycooling for sealing. A device to be used for sealing is not particularlylimited so far as it can perform a discharging operation of air and aheating operation. A device having a sealing treatment vessel forcontaining a laminate therein and capable of performing a dischargingoperation of air and a heating operation is preferably used. At thistime, it is preferable that a part or the whole of the sealing treatmentvessel is made of a gas non-permeable soft film. There can be employed aso-called single vacuum system in which the outside of a sealingtreatment vessel made of a gas non-permeable soft film is kept at theatmospheric pressure and a so-called double vacuum system in which thedegree of vacuum of the both of two chambers separated by a diaphragmmade of a gas non-permeable soft film can be adjusted. A single vacuumsystem is preferable in view of simple facilities. According to theproduction process of the first invention, it is possible to preventcell cracks even in a single vacuum system in which a load is applied inthe vertical direction of a laminate before melting of the sealingresin. A raw material of the foregoing film is not particularly limitedso far as it is a gas non-permeable soft film and has softness andstrength to a certain extent or more, to which when the inside of thefilm becomes in vacuo, an external air pressure is uniformly appliedover the whole of the laminate. Sheets or films of a rubber or a resincan be used.

The sealing treatment vessel of a single vacuum system may be oneintegrated with a heater, or one in which only a part thereof is made ofa gas non-permeable soft film. However, it is preferred to use a bag 14the whole of which is made of a gas non-permeable soft film. In thiscase, since the sealing treatment vessel is a mere bag, it can flexiblycorrespond in producing solar battery modules having various shapes andsizes. In particular, it is suitable for applications required forproducing products having various sizes such as building materials. Inintroducing the laminate 13 into the bag 14, it is preferred to coverthe entire periphery of the edge of the laminate 13 by a bleeder 20 madeof an air-permeable material, thereby not only preventing the moltenresin in the laminate 13 from flowing out but also securing a dischargeroute of air from the inside of the laminate 13. As the material to beused for the bleeder 20, cloths such as woven fabrics, knitting fabrics,and non-woven fabrics can be used.

In this way, in the case of using the bag 14 the whole of which is madeof a gas non-permeable soft film, plural bags 14 into which the laminate13 has been introduced can be arranged in a heating device. A pipe 15through which air can be discharged is connected to each of the bags 14and connected to a vacuum pump 17 via a pressure regulating valve 16.According to such a method, it is possible to perform a laminatingoperation for plural bags together by using a simple device.

After conducting the foregoing arrangement, the air between thetransparent panel 2 of the light reception surface side and the backface panel 3 is discharged, and heating is performed to melt the resin,followed by cooling for sealing. At this time, the temperatureconditions are not particularly limited, and it is only required thatthe temperature is raised to a temperature at which the resin can bemelted. In the case of a crystalline resin, it is only required that theresin is heated to the melting point thereof or higher. Also, in thecase where the sealing resin is a crosslinkable thermoplastic resin, thetemperature is raised to a temperature at which the crosslinking can beperformed and kept at that temperature for a prescribed period of time.The pressure is not particularly limited so far as the air in thelaminate 13 can be discharged, and the pressure can be reduced to anextent that the remaining of air bubbles can be lowered.

Above all, when the sealing resin is a crosslinkable thermoplasticresin, the sealing operation can be suitably carried out under thefollowing conditions. That is, it is preferred to carry out the sealingoperation including respective steps of a step of reducing the pressurein the sealing treatment vessel at a temperature at which thethermoplastic resin is not melted (step 1); a step in which thetemperature is raised to the vicinity of or higher than the meltingpoint of the thermoplastic resin in the reduced-pressure state (step 2);a step in which the pressure in the sealing treatment vessel is raised(step 3); a step in which the temperature is raised to a temperaturerange where a crosslinking reaction proceeds, thereby proceeding withthe crosslinking reaction (step 4); and a step in which cooling isperformed (step 5).

The foregoing step 1 is a step of reducing the pressure in the sealingtreatment vessel at a temperature at which the thermoplastic resin isnot melted. By reducing the pressure, the remaining of air bubbles isprevented. At this time, when the laminating device is of a singlevacuum system, since a load due to the atmospheric pressure is appliedin the vertical direction of the laminate 13 at the time of reducing thepressure, it is preferred to use the sealing resin sheet piece 11thicker than the thickness of the solar battery cell 4. In that case, ata temperature at which the thermoplastic resin is melted, the sealingresin sheet piece 11 can keep its shape. Therefore, a load is notapplied to the solar battery cell 4 so that the breakage of the solarbatter cell 4 can be prevented from occurring. As a result of reducingthe pressure in the step 1, the pressure in the sealing treatment vesselis suitably reduced from the atmospheric pressure (0.1 MPa) to 0.01 MPaor lower, and more suitably 0.005 MPa or lower. By thoroughly reducingthe pressure, it is possible to effectively prevent remaining of airbubbles from occurring.

The temperature at which the thermoplastic resin is not melted, asreferred to herein, refers to a temperature of the melting point orlower, suitably a temperature of at least 10° C. lower than the meltingpoint, and more suitably a temperature of at least 20° C. lower than themelting point. In the case where the thermoplastic resin does not have amelting point, one may think about it by replacing the melting point asreferred to herein by a softening point. In the pressure reductionoperation, the same temperature may be kept, or the temperature may beraised simultaneously. Though the elastic modulus of the resin isgradually lowered by the temperature rising, even when the temperaturedoes not reach the melting point, it is possible to thoroughly keep theshape at a temperature lower than the melting point to a certain extentor more. Accordingly, the temperature in the step 1 is suitably roomtemperature or higher and 50° C. or lower. In the step 1, across-sectional schematic view of the laminate 13 under reduced pressurein the case of using the sealing resin sheet piece 11 is illustrated inFIG. 2.

The step 2 is a step in which after reducing the pressure in the step 1,the temperature is raised to the vicinity of or higher than the meltingpoint of the thermoplastic resin in the reduced-pressure state. When thethermoplastic resin is subjected to temperature rising, the elasticmodulus is largely lowered in the vicinity of the melting point, wherebythe thermoplastic resin changes to a highly viscous liquid. The step 2is a step in which the thermoplastic resin is kept under a reducedpressure until the temperature reaches such a temperature range. In thestate that the elastic modulus is still high, when the degree of vacuumis reduced to raise the pressure, air flows into the laminate 13,whereby air bubbles may possibly remain in the sealing resin. Here, alower limit value of the temperature as reached in thetemperature-rising operation of the step 2 is suitably [(meltingpoint)−20]° C. or higher, more suitably [(melting point)−15]° C. orhigher, and further suitably [(melting point)−10]° C. or higher.

Also, an upper limit value of the temperature as reached in thetemperature-rising operation of the step 2 is usually a temperaturelower than the temperature range where the crosslinking reactionproceeds, suitably [(melting point)+50]° C. or lower, more suitably[(melting point)+30]° C. or lower, and further suitably [(meltingpoint)+20]° C. or lower. In the case where the temperature as reached istoo high, the resin is liable to flow too much, whereby the solarbattery cells may possibly move due to this matter. In particular, whenthe laminating device is of a single vacuum system, a load due to theatmospheric pressure is applied in the vertical direction of thelaminate 13 at the time of reducing the pressure, and the flow becomesremarkable, whereby the resin is likely flowed out from the edge of thelaminate 13.

It is preferable that a rate of raising the temperature in the step 2 isslow. The time required for raising the temperature from roomtemperature to the foregoing temperature is preferably 15 minutes orlonger, more preferably 30 minutes or longer, and further preferably onehour or longer. By slowly raising the temperature, it is possible toefficiently prevent cell cracks from occurring without causing rapidapplication of a load. In particular, in the case of using the sealingresin sheet pieces 11, this point of issue is important. At this time,the temperature-rising rate may be changed in the way, or a balancingoperation in which the temperature rising is stopped, thereby cancelinga temperature distribution in the laminate 13 may be carried out. Fromthe viewpoint of productivity, the time is usually 10 hours or shorter,and more suitably 3 hours or shorter. FIG. 3 is a cross-sectionalschematic view of the laminate 13 in the way of temperature rising byheating in the case of using the sealing resin sheet pieces 11 in thestep 2.

The step 3 is a step in which following the foregoing step 2, thepressure in the foregoing sealing treatment vessel is raised. Afterraising the temperature to the vicinity of or higher than the meltingpoint to melt or soften the resin, the degree of vacuum is reduced toraise the pressure. In this way, when the sealing resin is in the moltenor softened state, it is possible to prevent a phenomenon in which anexcessive pressure is applied in the vertical direction, whereby theresin undesirably flows within the laminate or flows out from the edge.

In the step 3, it is preferable that the pressure is slowly raised. Thetime required for raising the pressure is preferably 5 minutes orlonger, more preferably 10 minutes or longer, and further preferably 20minutes or longer. From the viewpoint of productivity, the time isusually 5 hours or shorter, and suitably 2 hours or shorter. Thepressure after the pressure rising is suitably 0.05 MPa or more, andmore suitably 0.07 MPa or more. The pressure can be also raised to thesame pressure (0.1 MPa) as the atmospheric pressure. At this time, thepressure rising may be carried out stepwise. In the step 3, thetemperature during raising the pressure is a temperature lower than thetemperature range where a cross-linking reaction proceeds, which is thetemperature employed in the step 4. Accordingly, the temperature isusually 120° C. or lower, and suitably 100° C. or lower.

Also, in the step 3, it is preferred to include a stage of raising thetemperature at the same time of raising the pressure in the foregoingsealing treatment vessel. In this way, it is possible to release thepressure applying to the laminate 13 step by step during the stage wherethe fluidity gradually increases, and therefore, it is effective toinhibit a phenomenon that the molten resin undesirably flows whilecontrolling the generation of residual air bubbles. In this case, it isdesired to set the temperature at the time of starting the pressurerising at from [(melting point)−10]° C. to [(melting point)+20]° C., andmore suitably from [(melting point)−5]° C. to [(melting point)+15]° C.and to raise the pressure during raising the temperature therefrom byfrom 3 to 30° C., and more suitably from 5 to 20° C. A ratio of thepressure-rising rate (MPa/min) to the temperature-rising rate (° C./min)is preferably from 0.001 to 0.1 (MPa/° C.), and more preferably from0.002 to 0.05 (MPa/° C.).

Also, it is preferable that after raising the pressure in the sealingtreatment vessel in the step 3, cooling is once performed, and thetemperature is then raised to the temperature range where a crosslinkingreaction proceeds in the step 4. Though after raising the pressure, thetemperature can be directly raised to the temperature range where acrosslinking reaction proceeds, a time for relaxing a residual stresscan be secured by once performing cooling, whereby it becomes possibleto more effectively inhibit flowing out of the molten resin, sinks(portions where the resin is defective in the edge) and movement ofcell. At this time, it is preferred to perform cooling to an extent thatthe resin thoroughly loses the fluidity. The cooling is suitablyperformed to [(melting point)−10]° C. or lower, and more suitably[(melting point)−20]° C. or lower.

After raising the pressure in the sealing treatment vessel as mentionedabove, the temperature is raised to the temperature range where acrosslinking reaction proceeds in the step 4, thereby proceeding withthe crosslinking reaction. The crosslinking reaction is made to proceedby heating usually at 100° C. or higher, suitably 120° C. or higher,more suitably 130° C. or higher, and further suitably 140° C. or higher.In order to prevent the deterioration of the resin, a crosslinkingtemperature of 200° C. or lower is usually employed. A time for keepingthe temperature range at which the crosslinking reaction proceeds variesdepending upon the target degree of crosslinking, etc. and is usuallyfrom 5 minutes to 2 hours, and suitably from 10 minutes to one hour.

When the crosslinking reaction proceeds in the step 4, the pressure inthe sealing treatment vessel is suitably 0.05 MPa or more, and moresuitably 0.07 MPa or more. By raising the pressure in the sealingtreatment vessel, it is possible to reduce the pressure to be applied inthe vertical direction. Since the crosslinking reaction proceeds at hightemperatures, the melt viscosity of the sealing resin at that time isconsiderably low as compared with the vicinity of the melting point. Forthat reason, it is important to inhibit movement of the cell and theflowing out of the resin without applying a undesirable pressure in thevertical direction at this time. However, in the case where the pressureis raised to the same pressure as the atmospheric pressure, sinks arepossibly generated depending upon the construction of the laminate.Therefore, it is suitable that the pressure is set lower than theatmospheric pressure at such time. Also, in the case where the pressureis raised to the same pressure as the atmospheric pressure, it becomesdifficult for the bleeder to compress the surrounding of the laminate,whereby the resin may possibly be flowed out. At such time, it is alsosuitable to set the pressure lower than the atmospheric pressure. Inthat case, it is preferable that the pressure is at least 0.001 MPalower than the atmospheric pressure, and suitably at least 0.01 MPa (inthis case, 0.09 MPa or lower) lower than the atmospheric pressure.Incidentally, the atmospheric pressure as referred to in the inventionrefers to the state that a pressurizing or pressure reduction operationis not positively applied. For example, even in the case where hot airis forcedly blown into an air heating furnace by a fan, whereby thepressure becomes slightly higher than the atmospheric pressure, thepressure is substantially identical with the atmospheric pressure.

After proceeding with the crosslinking reaction in the step 4, theprocess goes to the cooling step of the step 5. Usually, cooling isperformed to the vicinity of room temperature. When the cooling rate istoo fast, the glass may possibly be broken, and therefore, the coolingis suitably performed in 10 minutes or longer, and more suitably 30minutes or longer, thereby obtaining the solar battery module of theinvention. FIG. 4 is a cross-sectional schematic view of the laminate 13after cooling in the case of using the sealing resin sheet pieces 11 inthe step 5.

The thus obtained solar battery module is inhibited with respect toremaining of air bubbles, is inhibited with respect to flowing out ofthe resin from the edge, and is regularly arranged without causingbreakage of the plural solar battery cells. Since the solar batterymodule is regularly arranged and its appearance is beautiful, it issuitably used in outer walls, roofs, windows, etc. of various buildings.Since a suitable space is provided between the solar battery cells, thethus obtained solar battery module is especially suitably used as adaylighting type solar battery module.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional schematic view of one example of a solarbattery module of the invention.

FIG. 2 is a cross-sectional schematic view of a laminate under reducedpressure in the case of using sealing resin sheet pieces in the step 1.

FIG. 3 is a cross-sectional schematic view of a laminate in the way oftemperature rising by heating in the case of using sealing resin sheetpieces in the step 2.

FIG. 4 is a cross-sectional schematic view of a laminate after coolingin the case of using sealing resin sheet pieces in the step 5.

FIG. 5 is a planar schematic view showing that plural solar batterycells are arranged on a second sealing resin sheet.

FIG. 6 is a planar schematic view showing that lower sealing resin sheetpieces are arranged in a sheet piece arranging pattern A.

FIG. 7 is a planar schematic view showing that upper sealing resin sheetpieces are arranged in a sheet piece arranging pattern A.

FIG. 8 is a planar schematic view showing that lower sealing resin sheetpieces are arranged in a sheet piece arranging pattern B.

FIG. 9 is a planar schematic view showing that upper sealing resin sheetpieces are arranged in a sheet piece arranging pattern B.

FIG. 10 is an outline view of a sealing treatment vessel.

FIG. 11 is a diagram showing the temperature and the pressure at thetime of sealing treatment in Example 1.

FIG. 12 is a diagram showing the temperature and the pressure at thetime of sealing treatment in Example 2.

FIG. 13 is a diagram showing the temperature and the pressure at thetime of sealing treatment in Example 3.

In the foregoing drawings, 1 denotes a solar battery module; 2 denotes atransparent panel of the light reception surface side; 3 denotes a backface panel; 4 denotes a solar battery cell; 5 denotes a resin; 6 denotesa light reception surface; 7 denotes a back face; 8 denotes a conductor;9 denotes a space; 10 denotes a second sealing resin sheet; 11 denotes asealing resin sheet piece; 12 denotes a first sealing resin sheet; 13denotes a laminate; 14 denotes a bag; 15 denotes a pipe; 16 denotes apressure regulating valve; 17 denotes a vacuum pump; 18 denotes a lowersealing resin sheet piece; 19 denotes an upper sealing resin sheetpiece; 20 denotes a bleeder; 21 denotes an air heating furnace; and 22denotes a shelf, respectively.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention will be described below in more detail with reference tothe Examples. It should not be construed that the invention is limitedby these Examples.

EXAMPLE 1

Forty of square polycrystalline silicon solar battery cells of 125mm×125 mm×0.35 mm were used as the solar battery cell 4. Four cornersare chamfered by approximately several millimeters. A solder dip copperribbon wire manufactured by Marusho K.K. was used as the conductor 8.The ribbon wire has a width of 1.5 mm and a thickness of 0.25 mm. Solderis previously printed in a portion where the conductor 8 is bouned inlight reception surface 6 and the back face 7 of the solar battery cell4. One end of the conductor 8 was superimposed on a solder printingportion of the light reception surface 6 of the solar battery cell 4 andsoldered, and the other end was superimposed on a solder printingportion of the back face 7 of the adjacent solar battery cell 4 andsoldered. The cells adjacent to each other were connected to each otherby two conductors 8, and a distance thereof was set at 50 mm. That is,the width of the space 9 is 50 mm.

As the back face panel 3, a float plate tempered glass (blue sheetglass) of 1,000 mm×1,500 mm×10 mm was used. As the sealing resin sheet,“SOLAR EVA SC36” having a thickness of 0.6 mm, which is manufactured byHi-Sheet Industries, Ltd., was used. The sealing resin sheet is made ofa blend of an ethylene-vinyl acetate copolymer (EVA) with a crosslinkingagent, a silane coupling agent, a stabilizer, and the like, and theresin before crosslinking has a melting point, as measured by the DSCmethod, of 71° C. A shallow embossed pattern (satin finished pattern) isformed on one surface of the sealing resin sheet, and its depth is about45 μm. The sealing resin sheet was cut into a size of 1,000 mm×1,500 mm,two sheets of which were then superimposed on the back face panel 3.This two-sheet superimposed sealing resin sheet constructs the secondsealing resin sheet 10 having a thickness of 1.2 mm.

Plural solar battery cells 4 mutually connected to each other in theforegoing manner were placed on the second sealing resin sheet 10 andput in order lengthwise and breadthwise, thereby conducting thearrangement as illustrated in FIG. 5. The width of the space 9 betweenthe solar battery cells 4 adjacent to each other was set at 50 mm inboth the length and breadth directions. Also, a distance from the end ofthe solar battery cell 4 to the edge of the back face panel 3 was set at75 mm in the longitudinal direction (the direction in which the eightcells stand) and 87.5 mm in the width direction (the direction in whichthe five cells stand), respectively.

Subsequently, the sealing resin sheet piece 11 was arranged in asurrounding margin and in the space 9 between the solar battery cells 4.Here, two arrangement methods were studied in the present Example. Allof these methods are a method in which the lower sealing resin sheetpiece 18 is laid, and the upper sealing resin sheet piece 19 is thenlaid. The sheet piece arranging pattern A is a method in which the uppersealing resin sheet pieces 19 in the fragment form are arranged on thelower sealing resin sheet piece 18; and the sheet piece arrangingpattern B is a method in which the lower sealing resin sheet piece 18and the upper sealing resin sheet piece 19 are arranged intersected.

First of all, the sheet piece arranging pattern A will be described. Asillustrated in FIG. 6, the lower sealing resin sheet piece 18 wasarranged in a surrounding margin and in the space 9 between the solarbattery cells 4. The width of the lower sealing resin sheet piece 18 was25 mm between the solar battery cells 4 and 60 mm in the surroundingmargin in both the longitudinal direction and the cross direction,respectively. At this time, the lower sealing resin sheet was arrangedso as to press the conductor 8 in the position in the vicinity of thecenter between the solar battery cells 4 adjacent to each other. Byarranging the lower sealing resin sheet in the position in the vicinityof the center in this way, it is possible to minimize the transfer ofthe resin when melted and to prevent the breakage of the solar batterycell 4 or the conductor 8. Moreover, it is possible to prevent themovement of the solar battery cell 4 until melting. Here, though thesheet piece in the belt-like form was arranged, a punched sheet piecemay be used, too.

In addition, as illustrated in FIG. 7, the upper sealing resin sheetpiece 19 was arranged such that it was superimposed on the lower sealingresin sheet piece 18. The upper sealing resin sheet piece 19 to bearranged between the solar battery cells 4 adjacent to each other has asize of 25 mm×125 mm. The upper sealing resin sheet piece 19 to bearranged in the portion of sides of the surrounding margin has a size of60 mm×125 mm, and the upper sealing resin sheet piece 19 was alsoarranged in the corners.

By separately arranging the upper sealing resin sheet pieces 19, it ispossible to secure a passage in discharging the internal air and toprevent remaining of air bubbles from occurring. The thickness of thewhole of the sealing resin sheet pieces was 1.2 mm. At this time, it isalso possible to separately arrange the lower sealing resin sheet pieces18.

Next, the sheet piece arranging pattern B will be described. Asillustrated in FIG. 8, the lower sealing resin sheet piece 18 wasarranged in the space 9 between the solar battery cells 4 along with thesurrounding margin. The width of the lower sealing resin sheet piece 18was at 40 mm between the solar battery cells 4 and 60 mm in thesurrounding margin in both the longitudinal direction and the crossdirection, respectively. At this time, the lower sealing resin sheetpiece was arranged so as to press the conductor 8 in the position in thevicinity of the center between the solar battery cells 4 adjacent toeach other. By arranging the conductor 8 in the position in the vicinityof the center in this way, it is possible to minimize the transfer ofthe resin when melted and to prevent the breakage of the solar batterycell 4 or the conductor 8. Moreover, it is possible to prevent themovement of the solar battery cell 4 until melting. Here, though thesheet piece in the belt-like form was arranged, a punched sheet piecemay be used, too.

In addition, as illustrated in FIG. 9, the upper sealing resin sheetpieces 19 were arranged such that they were intersected on the lowersealing resin sheet piece 18. The width of the lower sealing resin sheetpieces 19 to be arranged in the space between the solar battery cells 4is 40 mm. The upper sealing resin sheet pieces 19 to be arranged in theportion of sides of the surrounding margin have a size of 60 mm×125 mm,and the upper sealing resin sheet pieces 19 were also arranged in thecorners. The total thickness of the sealing resin sheet pieces in theintersecting portion is 1.2 mm, and a load to be applied in the verticaldirection can be supported by this portion. Since the upper sealingresin sheet pieces 19 are separately arranged in the surrounding margin,and a space is present in other portions than the intersecting portions,it is possible to secure a passage in discharging the internal air andto prevent remaining of air bubbles from occurring.

In the case of the sheet piece arranging pattern B, since the transferamount of the molten resin is liable to become large as compared withthe sheet piece arranging pattern A, its performance is slightlyinferior from the viewpoint of preventing the movement of the solarbattery cell or the remaining of air bubbles. Accordingly, in the casewhere the sealing operation is difficult, such as the case where thearea of the module is large, the case where the thickness of thesubstrate is large, the case where the warp of the substrate is large,and the case where the space between the mutual solar battery cells islarge, it is preferred to employ the sheet piece arranging pattern A. Onthe other hand, the sheet piece arranging pattern B is preferable fromthe standpoint of productivity because the arranging works of sheetpieces are easy. Accordingly, the selection of these arranging patternswill be suitably made depending upon the purpose.

After arranging the sealing resin sheet piece 11 in this way, two sheetsof sealing resin sheets having been cut into a size of 1,000 mm×1,500 mmwere superimposed thereon. This two-sheet superimposed sealing resinsheet constructs the second sealing resin sheet 12 having a thickness of1.2 mm. A float plate tempered glass (white sheet glass) of 1,000mm×1,500 mm×10 mm was placed as the transparent panel 2 of the lightreception surface side thereon.

The entire periphery of the edge of the thus obtained laminate 13 wascovered by the bleeder 20, which was then put into the rubber-made bag14 as a sealing treatment vessel, followed by sealing the bag 14. Thereason why the edge of the laminate 13 is covered by the bleeder 20resides in the purposes of preventing the molten resin in the laminate13 from flowing out and securing a discharge route of air from theinside of the laminate 13.

Plural sets of the foregoing rubber-made bag 14 are laid on the shelves22 to be provided in the air heating furnace 21. Each of the rubber-madebags 14 is connected to the pipe 15 through which air can be discharged,which is connected to the vacuum pump 17 via the pressure regulatingvalve 16. The outline view of the sealing treatment device isillustrated in FIG. 10.

After setting in this way, the sealing treatment operation of thefollowing steps 1 to 5 was carried out. At this time, the temperatureand the pressure were controlled as shown in Table 1 and FIG. 11. Atthis time, the temperature is a temperature in the air heating furnace21, and the pressure is a pressure set by the pressure regulating valve16.

Step 1: “Step of Reducing the Pressure in the Sealing Treatment Vesselat a Temperature at which the Thermoplastic Resin is not Melted”

The temperature rising was started from room temperature (27° C.), andat the same time, the pressure reduction was started. About one minutelater, the pressure dropped to 0.005 MPa or lower.

Step 2: “Step of Raising the Temperature to the Vicinity of Or Higherthan the Melting Point of the Thermoplastic Resin in the ReducedPressure State”

Heating was continued such that the temperature reached 40° C. in 30minutes after starting the temperature rising; the temperature was keptat 40° C. for 10 minutes (balancing); the temperature was raised to 50°C. in 75 minutes; the temperature was kept at 50° C. for 10 minutes; thetemperature was raised to 60° C. in 105 minutes; the temperature waskept at 60° C. for 10 minutes; the temperature was raised to 71° C. (themelting point of EVA contained in the sealing resin sheet) in 120minutes; and the temperature was kept for 10 minutes.

Step 3: “Step of Raising the Pressure in the Sealing Treatment Vessel”

The temperature was raised from 71° C. to 90° C. in 90 minutes, and atthe same time, the pressure was raised from 0.005 MPa or lower to 0.09MPa in 90 minutes. At this time, a ratio of the pressure-rising rate(MPa/min) to the temperature-rising rate (° C./min) was 0.0047 (MPa/°C.). Thereafter, the system was kept at 90° C. for 30 minutes, cooled to40° C. in 60 minutes, and then kept at 40° C. for 30 minutes. Meanwhile,the pressure was kept at 0.09 MPa. Subsequently, a pressure was raisedto 0.1 MPa (atmospheric pressure) in about one minute, and the pressurereduction operation was completely stopped.

Step 4: “Step of Raising the Temperature to the Temperature Range wherea Crosslinking Reaction Proceeds, Thereby Proceeding with theCrosslinking Reaction”

Subsequently, the temperature was raised from 40° C. to 150° C. in 90minutes and kept at 150° C. for 40 minutes, thereby proceeding with thecrosslinking reaction.

Step 5: “Step of Performing Cooling”

Subsequently, cooling was performed from 150° C. to 40° C. in 60minutes. After keeping at 40° C. for 10 minutes, the resulting samplewas taken out from the air heating furnace 21.

TABLE 1 Treatment time Integrated time Temperature Pressure (min) (min)(° C.) (MPa) Step 1 1 1 27 → 40     0.1 → <0.005 Step 2 30 31 <0.005 1041 40 75 116 40 → 50 10 126 50 105 231 50 → 60 10 241 60 120 361 60 → 7110 371 71 Step 3 90 461 71 → 90 <0.005 → 0.09 30 491 90 0.09 60 551 90 →40 30 581 40 1 582  0.09 → 0.1 Step 4 90 672  40 → 150 0.1  40 712 150 Step 5 60 772 150 → 40  10 782 40

In all of the case of employing the sheet piece arranging pattern A andthe case of employing the sheet piece arranging material B, theresulting solar battery modules were quite free from occurrence of cellcracks or defects and breakage of the conductor and were not observedwith respect to remaining of air bubbles and the flowing out of thesealing resin or sinks in the surroundings. Also, the spaces between thesolar battery cells adjacent to each other all fell within the range of50±3 mm, and the solar battery cells were regularly arranged and sealed.

EXAMPLE 2

Solar battery modules were obtained in the same manner as in Example 1by employing the sheet piece arranging pattern A and the sheet piecearranging pattern B, except that the temperature and the pressure at thetime of the sealing treatment were changed as shown in Table 2 and FIG.12.

TABLE 2 Treatment time Integrated time Temperature Pressure (min) (min)(° C.) (MPa) Step 1 1 1 27 → 50     0.1 → <0.005 Step 2 30 31 <0.005 70101 50 → 71 30 131 71 14 145 71 → 74 Step 3 33 178 74 → 81 <0.005 → 0.0743 221 81 → 90 0.07 5 226 90 30 256 90 → 30 1 257 30 Step 4 30 287  30 →155 35 322 155  Step 5 30 352 155 → 30  1 353 30  0.07 → 0.1

In all of the case of employing the sheet piece arranging pattern A andthe case of employing the sheet piece arranging material B, theresulting solar battery modules were quite free from occurrence of cellcracks or defects and breakage of the conductor and were not observedwith respect to remaining of air bubbles and the flowing out of thesealing resin or sinks in the surroundings. Also, the spaces between thesolar battery cells adjacent to each other all fell within the range of50±3 mm, and the solar battery cells were regularly arranged and sealed.

In the present Example 2, it was successfully achieved to shorten thetime required for the sealing treatment to half or less time required inExample 1 by processing as fast as possible, in the steps in which thetime can be shortened. The productivity could be markedly enhancedwithout dropping the quality of the resulting product.

Also, in the present Example 2, the pressure in the step 4 was 0.07 MPa,the value of which was lower than that of Example 1 which wassubstantially the atmospheric pressure. While under the conditionsdescribed in Example 1, sinks in the surrounding or flowing out of theresin from the edge of the laminate was sometimes observed, this couldbe effectively prevented from occurring.

EXAMPLE 3

Solar battery modules were obtained in the same manner as in Example 1by employing the sheet piece arranging pattern A and the sheet piecearranging pattern B, except that the temperature and the pressure at thetime of the sealing treatment were changed as shown in Table 3 and FIG.13.

TABLE 3 Treatment time Integrated time Temperature Pressure (min) (min)(° C.) (MPa) Step 1 1 1 20 → 50     0.1 → <0.005 Step 2 30 31 <0.005 4576 50 → 71 30 106 71 14 120 71 → 74 Step 3 33 153 74 → 81 <0.005 → 0.0743 196 81 → 90 0.07 30 226 90 Step 4 30 256  90 → 155 35 291 155  Step 530 321 155 → 30  1 322 30  0.07 → 0.1

In all of the case of employing the sheet piece arranging pattern A andthe case of employing the sheet piece arranging material B, theresulting solar battery modules were quite free from occurrence of cellcracks or defects and breakage of the conductor and were not observedwith respect to remaining of air bubbles and the flowing out of thesealing resin or sinks in the surroundings. However, a part of thespaces between the solar battery cells adjacent to each other felloutside the range of 50±3 mm. Concretely, in the vicinity of the centerof the solar battery module, there was acknowledged a place where thespace between the solar battery cells adjacent to each other was lessthan 47 mm; and in the surrounding of the solar battery module, therewas acknowledged a place where the space between the solar battery cellsadjacent to each other exceeded 53 mm. However, it is not meant that aremarkable shift was found on the appearance, but the appearance wasuseful depending upon applications.

In Examples 1 and 2, the operation in which after raising the pressurein the sealing treatment vessel, cooling was once performed in the step3, and the temperature was raised to the temperature range where acrosslinking reaction proceeds in the step 4 was carried out. However,such an operation is omitted in the present Example 3. In this way,energy required for heating after once performing cooling could besaved. Also, the required time could be shortened even slightly ascompared with that in Example 2.

Industrial Applicability

According to the first invention, it is possible to provide a process ofproducing a solar battery module which, when plural solar battery cellsare arranged and sealed by a transparent resin, can prevent breakage ofthe solar battery cells from occurring. Also, according to the secondinvention, it is possible to provide a process of producing a solarbattery module having a good appearance, which can inhibit remaining ofair bubbles, movement of solar battery cells, or flowing out of thesealing resin from the edge. The modules which are produced according tothese production processes are useful as a daylighting type solarbattery module.

The invention claimed is:
 1. A process of producing a solar battery module comprising a solar battery cell sealed by a resin between a transparent panel of a light reception surface side and a back face panel, wherein the sealing resin comprises a crosslinkable thermoplastic resin, said process comprising: arranging a first sealing resin sheet substantially covering the entire surface of the transparent panel of the light reception surface side between the transparent panel of the light reception surface side and the solar battery cell, and arranging a second sealing resin sheet substantially covering the entire surface of the back face panel between the back face panel and the solar battery cell thereby forming an assembly which is then introduced into a sealing treatment vessel, and then performing a sealing operation comprising (i) reducing the pressure in the sealing treatment vessel to 0.01 MPa or lower at a temperature at which the thermoplastic resin is not melted; (ii) raising the temperature to the vicinity of or higher than the melting point of the thermoplastic resin in the reduced-pressure state; (iii) raising the pressure in the sealing treatment vessel to a pressure within a range of from 0.05 MPa to atmospheric pressure; (iv) raising the temperature to a temperature range where a crosslinking reaction proceeds, and proceeding with the crosslinking reaction while keeping the pressure in the sealing treatment vessel with the range of from 0.05MPa to atmospheric pressure; and (v) cooling, wherein the sealing treatment vessel comprises a bag and the entirety of the bag is made of a gas non-permeable soft film, a single vacuum system in which the outside of a sealing treatment vessel is kept at atmospheric pressure is employed, and the single vacuum system comprises plural bags arranged in a heating device.
 2. The process of producing a solar battery module according to claim 1, wherein the melting point of the thermoplastic resin is defined as Tm and the temperature as reached in the temperature-rising operation of (ii) is (Tm−20)° C. or higher and (Tm+50)° C. or lower.
 3. The process of producing a solar battery module according to claim 1, wherein in (iii), the temperature at which the pressure is raised is 120° C. or lower.
 4. The process of producing a solar battery module according to claim 1, wherein in (iii), the temperature rising is simultaneously carried out while raising the pressure in the sealing treatment vessel.
 5. The process of producing a solar battery module according to claim 4, wherein in (iii), a ratio of the pressure-rising rate (MPa/min) to the temperature-rising rate (° C./min) is from 0.001 to 0.1 (MPa/° C.).
 6. The process of producing a solar battery module according to claim 1, wherein in (iii), the pressure in the sealing treatment vessel is raised, and cooling is then once performed; and in (iv), the temperature is raised to a temperature range where the crosslinking reaction proceeds.
 7. The process of producing a solar battery module according to claim 1, wherein the solar battery module is a solar battery module including plural solar battery cells sealed by a resin, and the plural solar battery cells are arranged at a prescribed interval and mutually connected to each other by a conductor.
 8. The process of producing a solar battery module according to claim 1, wherein the thermoplastic resin is at least one resin selected from the group consisting of an ethylene-vinyl acetate copolymer, polyvinyl butyral, and polyurethane.
 9. The process of producing a solar battery module according to claim 1, wherein at least one of the transparent panel of the light reception surface side and the back face panel is made of a tempered glass or a double strength glass.
 10. The process of producing a solar battery module according to claim 1, wherein the produced solar battery module is a daylighting type solar battery module. 